When engine is cold/warm, it runs PERFECT. But 20-30 minutes into the driving (when engine is hot) it started to hesitate at low rpm and it backfires/misfires miserably with rough idle, it even stalled on me at times. This occur on a random basis.

What is the cause of this?

 

what do you mena engine is 'hot'? is it over heating?

 

i meant when the engine is warmed up normally, not over heat.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Spn_BB2 &raquo;</TD></TR><TR><TD CLASS="quote">what do you mena engine is 'hot'? is it over heating?</TD></TR></TABLE>

 

more info
do you have an aftermarket exhaust?
what kinda mods do you have?
it could be a number of things I would start with the egr valve on the front of the throttle body held in place my 2 10 mm bolts (I believe) take some carb cleaner and a toothbrush and clean all that built up black carbon out of your intake.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by specialedition &raquo;</TD></TR><TR><TD CLASS="quote">
it could be a number of things I would start with the egr valve on the front of the throttle body held in place my 2 10 mm bolts (I believe) take some carb cleaner and a toothbrush and clean all that built up black carbon out of your intake. </TD></TR></TABLE>

Yup, that's exactly what I first thought when I read this thread.

Also, check to see if you are throwing an engine codes.

 

My mods are stated in my sig.
I did that but the bogging still occur. I had my tranny swapped just recently and now Im using a chipped P13.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by specialedition &raquo;</TD></TR><TR><TD CLASS="quote">more info
do you have an aftermarket exhaust?
what kinda mods do you have?
it could be a number of things I would start with the egr valve on the front of the throttle body held in place my 2 10 mm bolts (I believe) take some carb cleaner and a toothbrush and clean all that built up black carbon out of your intake. </TD></TR></TABLE>

 

Im throwing a CEL with code 17, this refers to VSS.
However, my speedometer is working perfectly, but im going to swap my VSS anyway.


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AndyD &raquo;</TD></TR><TR><TD CLASS="quote">

Yup, that's exactly what I first thought when I read this thread.

Also, check to see if you are throwing an engine codes.</TD></TR></TABLE>

 

you are running a chipped program with a VAFC is this correct?
then I would say electrical , if you can unplug the VAFC start with it

 

My car runs lean 16.5:1 when the car is idling, so i have to bring the fuel up by roughly 10% via VAFC to make it 14.5

Now if I unplug the VAFC, how would I be able to tune the car from running too lean?

Or are you saying VAFC should not be connected with chipped ECU? Is this why Im running lean in low rpm/partial throttle?

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by specialedition &raquo;</TD></TR><TR><TD CLASS="quote">you are running a chipped program with a VAFC is this correct?
then I would say electrical , if you can unplug the VAFC start with it
</TD></TR></TABLE>

 

The only sensor problem I have right now is the VSS, the CEL throws the code 17.
Does that relate to the bogging?

My engine is running lean at idle and low rpm while partial throttle when warmed up, and that is when the bogging occurs. Even at cold it is running lean so I had to bring up the fuel via VAFC for the 1k-3k range.

I have tried 0% settings on VAFC, but it would be too lean and the bogging was real bad.


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Chase &raquo;</TD></TR><TR><TD CLASS="quote">

Good advise there....it sounds liek a ecu or sensor problem that is making the car run lean perhaps. The engine will run richer when its cold and lean out as it warms up...which could relate to your problem. </TD></TR></TABLE>

 

i had a very similar problem a few weeks ago and it was down to water getting down into 1 of the spark plugs, it was ok when cold (when i drive slowly) as soon as it warmed up and i put my foot down the problem started..... just a thought dont know if it will help

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by VSBB6 &raquo;</TD></TR><TR><TD CLASS="quote">When engine is cold/warm, it runs PERFECT. But 20-30 minutes into the driving (when engine is hot) it started to hesitate at low rpm and it backfires/misfires miserably with rough idle, it even stalled on me at times. This occur on a random basis.

What is the cause of this?</TD></TR></TABLE>

I had a similar problem. The cause of this is still unknown but I narrowed down the problem by eliminating: knocking, bad plugs, lean/rich condition etc. Neither of which was the case, but whenever it occured it seems as if my ecu went into "safe-mode." The bogging down would remain until I reset the ecu.

Through datalogging, I realised my ecu's spark advance remained very low and I would see negative numbers under sudden throttle inputs, or sudden load. It seems as if the ecu didn't like certain conditions, and tried to keep things safe, by retarding my timing ridiculously.

Since then I have uninstalled my Field SFC-VTEC controller, and the problem eventually cleared up.

 

My plugs are brand new, and the lean/rich doesn't solve the problem.
The ecu is not running "safe mode" in my case, it still allows me to rev over redline. The bogging ONLY gets better when I increase the fuel at narrow throttle.

Now if I leave all the VAFC settings at 0%, isn't that virtually the stock settings without the interference of the VAFC? Or the ECU will still pickup the signal and retard the timing?


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MUGEN_CF4 &raquo;</TD></TR><TR><TD CLASS="quote">

I had a similar problem. The cause of this is still unknown but I narrowed down the problem by eliminating: knocking, bad plugs, lean/rich condition etc. Neither of which was the case, but whenever it occured it seems as if my ecu went into "safe-mode." The bogging down would remain until I reset the ecu.

Through datalogging, I realised my ecu's spark advance remained very low and I would see negative numbers under sudden throttle inputs, or sudden load. It seems as if the ecu didn't like certain conditions, and tried to keep things safe, by retarding my timing ridiculously.

Since then I have uninstalled my Field SFC-VTEC controller, and the problem eventually cleared up.</TD></TR></TABLE>

 

interesting - so bump.

 

it is very hard to say --- I am NOT a Fan of the VAFC product...
If you have the original p13 then I would use it and eliminate the VAFC
start from that point --- or just use your stand alone chipped ecu if it still does it then you know you have some other problem so check the codes --- make sure if you change ecus that you unplug the neg. battery cable FIRST
I would also recheck the pinout codes for the ecu to make sure everything is where it is suppose to be. Then I would plug in the ecu, plug the neg. battery back up and start the car if you get a check engine light then more than likely it is a bad sensor.
It can be hard to diagnose your problem cause of the chipped ecu ...
it depends on what modifications where done to your stock ecu what they reprogramed --- From what I read though it sounds kinda like it could be the modifications within the ecu that is making you run lean
where did you get it and what program is it?

 

i Had the same problem and replaced knock sensor, tps,plugs and plug wires and still did the same thing. So i went to a p28 and now runnning uberdata and have no problems anymore.

 

Is the computer OBD II or OBD I? OBD II computers tend to be very picky. Try to keep "sensor readings" consistent.

If these ECUs detect drastic inconsistent values/changes, they tend to complain, by running very weak base maps (especially timing).